The invention relates to a structural motor vehicle axle system assembled by structural bonding and the method of assembly thereof. The invention relates more particularly to torsionally flexible axle systems.
Currently, torsionally flexible axle systems are made of steel assembled by arc welding. This structure is economical and confers good performance to the axle system but has the drawback of being of greater weight and of causing alterations to the mechanical properties of the materials in the assembly zone due to the welding.
Lightweight axle systems are known, comprising longitudinal arms made of aluminum, articulated by means of pivots in order to avoid producing stresses in the assembly zones. This structure has the drawback of complicating the kinematics of the parts and of increasing the cost of the assembly.
The document EP-1 036 680 discloses a lightweight axle system formed by arms molded in aluminum and a cross bracing made of steel. The cross bracing is fitted into the arms, and a space made between the cross bracing and the arms is filled with adhesive. The joint is then compressed to complete the assembly. This compression step creates stresses in the assembled materials and in the adhesive which may lead to an embrittlement of the assembly. Moreover, this joint requires tight manufacturing tolerances in addition to the use of anaerobic adhesives which do not have optimal behavior, in particular in order to avoid scraping off the adhesive during the assembly of the two parts.
A further document U.S. Pat. No. 6,099,084 discloses a lightweight axle system formed by a cross bracing made of aluminum assembled by a force fit and possibly binding, in the suspension arms. In this case, the fit also creates significant stresses which may result in an embrittlement of the assembly zones and requires tight manufacturing tolerances and the use of anaerobic adhesives for the same reasons as the previous document. Moreover, the tightening torque which is obtained is limited.